1. Field of the Invention
The present invention relates to heartbeat detection devices. In particular, the present invention relates to a heartbeat detection device transmitting, by radio, to a separate receiver, a signal concerning heartbeat detected by electrodes.
2. Description of the Background Art
U.S. Pat. No. 5,491,474 for example discloses a heartbeat detection device transmitting, by radio, to a receiver, information about an electric potential detected by electrode(s) in electrical contact with the chest of a subject, the information being transmitted in the form of heartbeat signals, for display and storage for example of the transmitted data.
One of conventional heartbeat detection devices, disclosed in the above-described U.S. patent, is described now. As shown in FIGS. 11 and 12, a heartbeat detection device 101 includes a predetermined casing 106 having electrodes and a transmitter, and a belt 108 for fastening purpose is attached to the longitudinal ends of casing 106 so that casing 106 can be mounted on the chest.
Casing 106 is plastic in nature. As shown in FIG. 13, within casing 106 mounted on and accordingly facing the chest, two electrodes 104 in electrical contact with the chest are provided with a certain distance therebetween. Between these two electrodes 104, as shown in FIG. 12, a transmitter 102 is provided that is electrically connected to electrodes 104 for transmitting signals detected by electrodes 104 to a receiver (not shown).
Belt 108 is fastened to allow casing 106 which is now a part of belt 108 to be brought into intimate contact with the chest, so that two electrodes 104 electrically contact two different areas on the chest to detect the potential difference therebetween. The detected potential difference is provided to transmitter 102 and transmitter 102 then transmits to the receiver the potential difference in the form of signals concerning heartbeat.
The above-described conventional heartbeat detection device 101, however, has some problems. Specifically, since two electrodes 104 as well as transmitter 102 relatively heavier than electrodes 104 are included in one casing 106, this casing 106 is likely to vibrate or swing as the body of the subject with the detection device mounted thereon moves. Swinging of casing 106 eventually causes electrodes 104 to swing together, leading to a problem that accurate signals concerning heartbeat cannot be detected due to changes in position of contact of electrodes 104.
Further, the plasticity of casing 106 is not enough to ensure the contact of electrodes 104 with predetermined areas. In order to surely bring electrodes 104 into contact with predetermined areas, belt 108 must be fastened to a considerable degree so that casing 106 is hardly pressed against the chest, leading to a problem that the subject could feel tight.